Embodiments relate to a light emitting device, a light emitting device package and a lighting system including the same.
Nitride semiconductors are attracting much attention for the fields of optical devices and high-power electronic devices because of their high thermal stability and wide band gap energy. In particular, blue light emitting devices (LEDs), green LEDs, and UV LEDs that use nitride semiconductors have been commercialized and are being widely used.
In recently, LEDs are used as light sources of display devices, indoor and outdoor lightings, and vehicle head lamps. It is necessary to improve an optical power of the LEDs to apply the LEDs to various high-power electronic devices.
According to a related art LED, injected electrons and holes are not uniformly supplied within an LED, but concentrately supplied to a specific portion or recombined with each other. Thus, current is not smoothly supplied to the other portion to cause current crowding.
The partial concentration of the current may apply a large stress to the LED as well as deteriorate light emission uniformity. The current crowding may cause serious limitations as a supply amount of the current increases. That is, when current above a predetermined level is applied, light efficiency is not constantly maintained, but reduced. A relation between the applied current and an optical power does not linearly increase. As a large amount of current is applied more and more, a further large amount of heat is generated. When the further large amount of the heat is partially generated, performance and life cycle of the LED may be degraded. Also, such phenomenon may get worse because large-sized LED or a high-power LED is operated under high current.